1. Field of the Invention
This invention relates to an automatic control unit that improves the power factor on electric lines subject to reactive loading, and more particularly, it relates to a system that adjusts capacitive reactance connected to electric lines.
2. Description of Prior Art
It is common place in most electric power lines, as for example the single phase two wire circuit, which serves a multitude of consumers for reactive loads to produce an unfavorable power factor. Stated in a different manner, air conditioners and heat pumps, air compressors and water pumps, etc. are large inductive reactances connected to power lines. The power factor can be adversely effected to a degree by these loads that the power companies apply a surcharge to power users adding large inductive loads to their power distribution system.
More particularly, the unit of reactive power in a circuit carrying sinusoidal current when the product of the root-mean-square value of the voltage, expressed in volts, by the root-means-square value of the current, expressed in amperes, and the sign of the phase angle between the voltage and current equals 1. This unit is abreviated as var, which is the unit for the commonly denoted term of the reactive volt-ampere.
Generally, some compensation must be provided the electric power lines whenever the var units deteriorate to a value of approximately 60% of the ideal. For this purpose, several automatic control systems exist which add or remove capacitors from the electric power lines in an attempt to bring the var unit value towards one. Many of these units operate automatically with fixed incremental additions of capacitance. Other units are semi-automatic with some manual attention required to insure that an excess amounts of capacitance were added to the power lines and thereby inducing a capacitive reactance problem to the electric power lines.
The present automatic var control unit is fully automatic but it can be operated manually and in either operating mode provides new functions and features not found in prior var control devices. More particularly, the present controller only responds to the actual var value on the electric lines and makes the addition or removal of capacitance from a capacitor bank on the lines in either series or binary progressions of programmed capacitance magnitudes. In addition, the present controller permits ready manual operation, if needed, with a direct visual readout of the watt and var condition values and the capacitors upon the electrical power lines.